Narrow Band Internet of Things (NB-IoT) is a narrowband (180 KHz bandwidth) system being developed for the cellular internet of things by 3GPP. The system is based on LTE systems and addresses optimized network architecture and improved indoor coverage for a massive number of devices with any one or more of the following characteristics:                low throughput devices (e.g., 2 Kbps)        low delay sensitivity (e.g., ˜10 seconds)        ultra-low device cost (e.g., below 5 dollars)        low device power consumption (e.g., battery life of 10 years)        
It is envisioned that each cell (e.g., ˜1 km2) in this system will serve thousands (e.g., ˜50 thousand) of wireless devices such as sensors, meters, actuators, etc. It is imperative that this system can provide good coverage for its devices, which often are located deep indoors e.g. underground in basements, or even built into walls of a building and with limited or no possibility for battery charging. Although many different types of devices are envisioned, for the sake of simplicity they will be referred to as wireless devices (WDs) or user equipments (UEs) throughout this document.
In order to make it possible to deploy NB-IoT using only one refarmed GSM carrier and support lower manufacturing costs for NB-IoT UEs, the bandwidth has been reduced to one physical resource block (PRB) of size 180 KHz divided into several subcarriers. For frequency division duplex or FDD (i.e. the transmitter and the receiver operate at different carrier frequencies), only half-duplex mode needs to be supported in the UE. The lower complexity of the devices (e.g., only one transmission/receiver chain) means that some repetition might be needed also in normal coverage. Further, to alleviate UE complexity, the working assumption is to have cross-subframe scheduling. That is, a transmission is first scheduled on an Enhanced Physical DL Control Channel (E-PDCCH, also known as NB-PDCCH) and then the first transmission of the actual data on the Physical DL Shared Channel (PDSCH) is carried out after the final transmission of the NB-PDCCH. Similarly, for uplink (UL) data transmission, information about resources scheduled by the network and needed by the UE for UL transmission is first conveyed on the NB-PDCCH, and then the first transmission of the actual data by the UE on the Physical UL Shared Channel (PUSCH) is carried out after the final transmission of the NB-PDCCH. In other words, for both cases above, there is no simultaneous reception of control channel and reception/transmission of data channel from the UE's perspective.
The following text is an excerpt from section 7 of 3 GPP TS 36.304, the entirety of which is herein incorporated by reference:                7. Paging        7.1 Discontinuous Reception for paging        The UE may use Discontinuous Reception (DRX) in idle mode in order to reduce power consumption. One Paging Occasion (PO) is a subframe where there may be P-RNTI transmitted on PDCCH addressing the paging message. One Paging Frame (PF) is one Radio Frame, which may contain one or multiple Paging Occasion(s). When DRX is used the UE needs only to monitor one PO per DRX cycle.        PF and PO is determined by following formulae using the DRX parameters provided in System Information:        PF is given by following equation:SFN mod T=(T div N)*(UE_ID mod N)        Index i_s pointing to PO from subframe pattern defined below will be derived from following calculation:i_s=floor(UE_ID/N)mod Ns         System Information DRX parameters stored in the UE shall be updated locally in the UE whenever the DRX parameter values are changed in SI. If the UE has no IMSI, for instance when making an emergency call without USIM, the UE shall use as default identity UE_ID=0 in the PF and i_s formulas above.        The following Parameters are used for the calculation of the PF and i_s:                    T: DRX cycle of the UE. T is determined by the shortest of the UE specific DRX value, if allocated by upper layers, and a default DRX value broadcast in system information. If UE specific DRX is not configured by upper layers, the default value is applied.            nB: 4T, 2T, T, T/2, T/4, T/8, T/16, T/32.            N: min(T,nB)            Ns: max(1,nB/T)            UE_ID: NISI mod 1024.                        IMSI is given as sequence of digits of type Integer (0 . . . 9), IMSI shall in the formulae above be interpreted as a decimal integer number, where the first digit given in the sequence represents the highest order digit.        For example:IMSI=12(digit1=1,digit2=2)        In the calculations, this shall be interpreted as the decimal integer “12”, not “1×16+2=18”.        7.2 Subframe Patterns        FDD:        
TABLE 0-1PO when PO when PO when PO when Nsi_s = 0i_s = 1i_s = 2i_s = 319N/AN/AN/A249N/AN/A40459                TDD (all UL/DL configurations):        
TABLE 0-2PO when PO when PO when PO when Nsi_s = 0i_s = 1i_s = 2i_s = 310N/AN/AN/A205N/AN/A40156